How to call a method after bean initialization is complete?

Question

I have a use case where I need to call a (non-static) method in the bean only-once at the ApplicationContext load up. Is it ok, if I use MethodInvokingFactoryBean for this? Or we have a some better solution?

As a side note, I use ConfigContextLoaderListener to load the Application Context in web application. And want, that if bean 'A' is instantiated just call methodA() once.

How can this be done nicely?

Answer 1

You can use something like:

<beans>
    <bean id="myBean" class="..." init-method="init"/>
</beans>

This will call the "init" method when the bean is instantiated.

Answer 2

To expand on the @PostConstruct suggestion in other answers, this really is the best solution, in my opinion.

• It keeps your code decoupled from the Spring API (@PostConstruct is in javax.*)
• It explicitly annotates your init method as something that needs to be called to initialize the bean
• You don't need to remember to add the init-method attribute to your spring bean definition, spring will automatically call the method (assuming you register the annotation-config option somewhere else in the context, anyway).

Answer 3

There are three different approaches to consider, as described in the reference

Use init-method attribute

Pros:

• Does not require bean to implement an interface.

Cons:

• No immediate indication this method is required after construction to ensure the bean is correctly configured.

---

Implement InitializingBean

Pros:

• No need to specify init-method, or turn on component scanning / annotation processing.
• Appropriate for beans supplied with a library, where we don't want the application using this library to concern itself with bean lifecycle.

Cons:

• More invasive than the init-method approach.

---

Use JSR-250 @PostConstruct lifecyle annotation

Pros:

• Useful when using component scanning to autodetect beans.
• Makes it clear that a specific method is to be used for initialisation. Intent is closer to the code.

Cons:

• Initialisation no longer centrally specified in configuration.
• You must remember to turn on annotation processing (which can sometimes be forgotten)

Answer 4

Have you tried implementing InitializingBean? It sounds like exactly what you're after.

The downside is that your bean becomes Spring-aware, but in most applications that's not so bad.

Answer 5

You could deploy a custom BeanPostProcessor in your application context to do it. Or if you don't mind implementing a Spring interface in your bean, you could use the InitializingBean interface or the "init-method" directive (same link).

Answer 6

To further clear any confusion about the two approach i.e use of

1. @PostConstruct and
2. init-method="init"

From personal experience, I realized that using (1) only works in a servlet container, while (2) works in any environment, even in desktop applications. So, if you would be using Spring in a standalone application, you would have to use (2) to carry out that "call this method after initialization.